1. Field of the Invention
The present invention relates to a heat sink for cooling an electronic device mounted to a printed circuit board, and in particular to a surface mounted collector plate which is in direct thermal contact with a CPU.
2. Description of the Related Art
The current collector plate incorporates features for mounting to a printed circuit board, thermal contact with a CPU and heat spreading, and connection to a heat pipe all in a single part. This requires multiple machining steps and plating on a monolithic part.
Referring to FIGS. 1A and 1B, a CPU 12 is mounted to a PCB 10 which is provided with studs 14 for mounting a heat collector 20 including a mounting plate 25 having tabs 22 and holes 23 for receiving the studs 14. The collector 20 is also provided with parallel ridges 24 defining a central channel 26 which receives a heat pipe 16 connected to a heat dissipator 18 having cooling fins. It is partially filled with liquid which undergoes a cycle of condensation and evaporation between the collector 20 and the heat dissipator 18. The pipe may be received in the channel in a press-fit, or it may be soldered or held by thermally conductive bonding, whereupon a cover plate 28 is soldered or bonded in place to improve heat transfer. The pipe 16 is shown having a closed end, buy may also be part of a conventional cooling loop.
FIGS. 2A to 2C show the steps which are necessary to produce the unitary heat collector 20 and mounting plate 20 according to the prior art. FIG. 2A shows a machined or extruded block of metal 21 having a pair of ridges 24 upstanding from a plate 25 and flanking a central channel 26, and an inset 27 for receiving a cover plate. Whether the block is machined or extruded depends on the material; copper is not as readily extruded as aluminum. The material chosen depends on the desired properties such as cost, weight, thermal conductivity, extrudability, and solderability. The block of FIG. 2A is milled to enlarge the base plate 25 at both ends of the ridges 24 (FIG. 2B). The plate 25 is then milled to form the tabs 22 and drilled to form the holes 23 (FIG. 2C).
FIG. 3A shows the first step in producing a unitary pin fin type heat sink according to the prior art, wherein a plate 32 having upstanding ribs 33 is extruded. FIG. 3B shows the second step, wherein the ribs are machined or gang-sawed to produce pins 34. As shown in FIG. 3C, the plate is then machined to produce tabs 36, and the tabs are drilled to produce holes 38.